The present invention relates generally to an impact dot printer, and in particular to an impact dot print head utilizing a coil magnet to effect printing.
Impact dot print heads are known in the art and contain a ring-shaped permanent magnet for maintaining a print armature in a non-print position. A plurality of electromagnets corresponding to each armature are positioned within the ring-shaped permanent magnet to cancel the magnetic force of the permanent magnet allowing printing. The electromagnets are positioned adjacent each other in a ring.
When a plurality of electromagnets are excited at the same time, a flux generated by the electromagnet travels through the cores of neighboring electromagnets. The flux travels in a direction which prevents the release of the armature so that the armature is insufficiently released providing an insufficient print force causing deterioration of print quality. This problem is one of magnetic interference.
To solve this problem in a conventional impact dot print head, a large amount of electrical energy is supplied to the electromagnets to reduce the influence of magnetic interference from adjacent magnetic cores. However, this method suffers from the disadvantage that it requires a large sized power source increasing the cost of the printer as well as limiting the printing operation due to the generation of heat from the electromagnets.
Accordingly, it is desired to provide an impact dot print head which overcomes the disadvantages of the prior art devices described above.